Gas Exchange II - Mechanisms of Ventilation 1

Frage	Antworten
How is ventilation achieved?	Via convection of the respiratory medium over the gas exchange surfaces
What gradient does this maintain?	Maintains a partial pressure gradient at the respiratory interface so fresh O2 is delivered and CO2 is removed.
What mechanical force is applied to achieve ventilation?	Active muscle force, which is applied to the relaxed respiratory system.
What is the key step in ventilation?	The act of inspiration
What is Boyle's Law?	P1V1=P2V2 So as volume in thorax increases, pressure in interpleural layer falls.
Draw a diagram showing the process of Inspiration	Active process Volume of thorax is increased as diaphragm contracts and external intercostal muscles contract.
INSPIRATION	Vol. thorax ^ shown by change in tidal volume. Pressure in interpleural space starts off negative w.r.t atmospheric pressure. As pressure becomes even more negative it causes alveoli to expand, their volume decreases below atmospheric pressure. As a result of pressure in alveoli at the end of the bronchilar tree becoming sub-atmospheric as air molecule mol/L stays the same, a pressure gradient is created. Air flows into lungs until alveolar presusure=atmospheric pressure.
EXPIRATION VOLUME CHANGES	RECOIL Volume decrease RIBCAGE RELAX Volume decrease
EXPIRATION PRESSURE CHANGES	Intrapleural P ^ as vol. of ipl decrease Distention removed Recoil palv>patm Bulk flow down p' out of lungs
Why F.R.C and P.O.I known as the static property of the lungs?	As there's no air movement in/out of the lungs btw F.R.C and P.O.I
What is compliance?	A value showing the elasticity and distention of the lungs c=dV/dP
Dynamic Pressure-Volume Relationship, inspiration.	Right deviation Resistive forces which oppose airflow. Greater pressure required to get air into the lungs.
Name the types of resistance affecting inspiration (3)	Airway resistance Pulmonary tissue resistance Inertia of air and tissues
Why do they assist?	As an elastic system always resists perturbation from its relaxed state.
Dynamic Pressure-Volume relationship - Expiration	Curve deviates to the left Resistive forces assist airflow.
Resistive forces for expiration	Elastic recoil of lungs and chest wall Surface tension in alveolar surfactants
When can expiration be active?	during forced exhalation as internal intercostal muscles and abdominal muscles contract.
Describe ventilation in birds	Air moves through lungs from interconnected air sacs which do not participate in Gx as they don't have a rich blood supply.
Describe ventilation in frogs	A positive pressure gradient as air has to be forced into the lungs
Describe airway movements in insects	Spiracles line each body segment and penetrate within to allow direct diffusion between air and tissues of the body.
Bellow	In larger insects contraction of abdominal muscles 'pump' air through tracheae.

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Gas Exchange II - Mechanisms of Ventilation 1

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